The thrombin inhibitor, used in the formulation of the present invention is a low molecular weight drug with pH dependent solubility. It is characterised by a low solubility at basic pH which is dramatically increased in the protonated form at acidic pH. Thus, upon administration in conventional IR formulations, fast dissolution of the drug is obtained in acidic pH while markedly slower dissolution is obtained at more neutral pH. This variability in dissolution is not acceptable for safe, efficient and convenient therapy. The present invention provides an immediate release formulation based on conventional manufacturing processes with careful chosen excipients that provides a dissolution which is not, or very little dependent on pH.
Several different ways have been suggested in order to prepare immediate-release solid dosage forms.
Lachman (The theory and practice of industrial pharmacy 1986, 343, appA) describes the composition and manufacturing of two different standard granulates for IR tablets. These two compositions gave very poor quality of the granulates, which gave unacceptable tablets with very low hardness. These compositions do not work with the low molecular weight thrombin inhibitors used in connection with the present invention. The tablets do not answer to the definition of a rapidly dissolving drug product presented in Guidance for Industry. Waiver of in Vivo Bioavailability and Bioequivalens Studies for Immediate Release Solids Dosage Forms Containing Certain Active Moieties/Active Ingredients Based on Biopharnaceutics Classification System. Tablets must release 85% or more of stated amount within 30 min.